Direct Spells:
Spellcasting + Magic [Force] to cast. DV is equal to Hits. It's resisted with just Willpower or Body.
Indirect Spells:
Singe Target Indirect Spells are cast using Spellcasting + Magic [Force] vs Reaction + Intuition. Net hits by the caster add to DV, more hits by defender lead to a miss and no damage.
Area Indirect spells are like grenades, in that they are targeted at a location rather than a person, and require a Spellcasting + Magic [Force] (3) test or they scatter. Hits above 3 add to DV and hit everything in the area.
Spell damage is resisted by Body + Armor, with an AP modifier equal to the Force of the Spell. Armor Mods such as non-conductivity add their rating to the armor to resist their damage type.
So yes, a Direct Combat spell will often do less damage. But it's also a much more sure thing, and is less likely to be resisted.
Indirect Spells can be dodged or have a chance to scatter, are resisted by more dice, and can even have specialized armor to add even more damage resistance.